International Mobile Telecommunications-Advanced (IMT Advanced), 4th Generation, is the next technological strategy in the field of wireless communications. A 4G system will upgrade existing communication networks and is expected to provide a comprehensive and secure IP based solution where facilities such as voice, data and streamed multimedia will be provided to users on an "Anytime, Anywhere" basis and at much higher data rates compared to previous generations.
This article deals with the evolution and concepts of a 4th Generation Wireless Communication System.
Features of 4G Wireless Systems
4G is being developed to accommodate the QOS and rate requirements set by forthcoming applications like wireless broadband access, Multimedia Messaging Service (MMS), video chat, mobile TV, HDTV content, Digital Video Broadcasting (DVB), minimal services like voice and data, and other services that utilize bandwidth.
- A spectrally efficient system (in bits/s/Hz and bits/s/Hz/site).
- High network capacity: more simultaneous users per cell.
- A nominal data rate of 100 Mbit/s while the client physically moves at high speeds relative to the station, and 1 Gbit/s while client and station are in relatively fixed positions as defined by the ITU-R.
- A data rate of at least 100 Mbit/s between any two points in the world.
- Smooth handoff across heterogeneous networks.
- Seamless connectivity and global roaming across multiple networks.
- High quality of service for next generation multimedia support (real time audio, high speed data, HDTV video content, mobile TV, etc).
- Interoperability with existing wireless standards.
- An all IP, packet switched network.
Motivation for 4G Research Before 3G Has Not Been Deployed?
- 3G performance may not be sufficient to meet needs of future high-performance applications like multi-media, full-motion video, wireless teleconferencing. We need a network technology that extends 3G capacity by an order of magnitude.
- There are multiple standards for 3G making it difficult to roam and interoperate across networks. we need global mobility and service portability
- 3G is based on primarily a wide-area concept. We need hybrid networks that utilize both wireless LAN (hot spot) concept and cell or base-station wide area network design.
- We need wider bandwidth.
- Researchers have come up with spectrally more efficient modulation schemes that can not be retrofitted into 3G infrastructure
- We need all digital packet networks that utilize IP in its fullest form with converged voice and data capability.
Internet Speeds
2.5G is the interim solution for current 2G networks to have 3G functionality. 2.5G networks are being designed such that a smooth transition (software upgrade) to 3G can be realized.2.5G networks currently offer true data speeds up to 28kbps.
In comparison, the theoretical speed of 3G can be up to 2 Mbps, i.e., approximately 200 times faster than previous 2G networks. This added speed and throughput will make it possible to run applications such as streaming video clips. It is anticipated that 4G speeds could be as high as 100 Mbps. Thus, 4G will represent another quantum leap in mobile Internet speeds and picture quality.
4G could bring connection speeds of up to 50 times faster than 3G.
4G Applications
One of the most notable advanced applications for 4G systems is location based services. 4G location applications would be based on visualized, virtual navigation schemes that would support a remote database containing graphical representations of streets, buildings, and other physical characteristics of a large metropolitan area. This database could be accessed by a subscriber in a moving vehicle equipped with the appropriate wireless device, which would provide the platform on which would appear a virtual representation of the environment ahead.
For example, one would be able to see the internal layout of a building during an emergency rescue. This type of application is sometimes referred to as "Telegeoprocessing", which is a combination of Geographical Information Systems (GIS) and Global Positioning Systems (GPS) working in concert over a high-capacity wireless mobile system.
Telegeoprocessing over 4G networks will make it possible for the public safety community to have wireless operational functionality and specialized applications for everyday operations, as well as for crisis management.
The emergence of next generation wireless technologies will enhance the effectiveness of the existing methods used by public safety.
3G technologies and beyond could possibly bring the following new features to public safety:
Virtual navigation
As described, a remote database contains the graphical representation of streets, buildings, and physical characteristics of a large metropolis. Blocks of this database are transmitted in rapid sequence to a vehicle, where a rendering program permits the occupants to visualize the environment ahead. They may also "virtually" see the internal layout of buildings to plan an emergency rescue, or to plan to engage hostile elements hidden in the building.
Tele-medicine
A paramedic assisting a victim of a traffic accident in a remote location could access medical records (e.g.-rays) and establish a video conference so that a remotely based surgeon could provide “on-scene” assistance. In such a circumstance, the paramedic could relay the victim's vital information (recorded locally) back to the hospital in real time, for review by the surgeon.
Crisis-management applications
These arise, for example, as a result of natural disasters where the entire communications infrastructure is in disarray. In such circumstances, restoring communications
quickly is essential. With wideband wireless mobile communications, both limited and complete communications capabilities, including Internet and video services, could be set up in a matter of
hours. In comparison, it may take days or even weeks to re-establish communications capabilities when a wire line network is rendered inoperable.
Comparing Key Parameters of 4G with 3G
| 3G | 4G | |
| Major Requirement Driving Architecture | dominantly voice driven - data was always add on | Converged data and voice over IP |
| Network Architecture | Wide area cell-based | Hybrid - Integration of Wireless LAN (WiFi, Bluetooth) and wide area |
| Speeds | 384 Kbps to 2 Mbps | 20 to 100 Mbps in mobile mode |
| Frequency Band | Dependent on country or continent (1800-2400 MHz) | Higher frequency bands (2-8 GHz) |
| Bandwidth | 5-20 MHz | 100 MHz (or more) |
| Switching Design Basis | Circuit and Packet | All digital with packetized voice |
| Access Technologies | W-CDMA, 1xRTT, Edge | OFDM and MC-CDMA (Multi Carrier CDMA) |
| Forward Error Correction | Convolutional rate 1/2, 1/3 | Concatenated coding scheme |
| Component Design | Optimized antenna design, multi-band adapters | Smarter Antennas, software multiband and wideband radios |
| IP | A number of air link protocols, including IP 5.0 | All IP (IP6.0) |
Limitations of 4G
Although the concept of 4G communications shows much promise, there are still limitations that must be addressed.
Operating area
Although 2G networks are becoming more ubiquitous, there are still many areas not served. Rural areas and many buildings in metropolitan areas are not being served well by existing wireless networks. This limitation of today’s networks will carry over into future generations of wireless systems.
The hype that is being created by 3G networks is giving the general public unrealistic expectations of always on, always available, anywhere, anytime communications. The public must realize that although high-speed data communications will be delivered, it will not be equivalent to the wired Internet – at least not at first. If measures are not taken now to correct perception issues, when 3G and later 4G services are deployed, there may be a great deal of disappointment associated with the deployment of the technology, and perceptions could become negative. If this were to happen, neither 3G nor 4G may realize its full potential.
Cost
The equipment required to implement a next generation network is still very expensive. Carriers and providers have to plan carefully to make sure that expenses are kept realistic.
One technique currently being implemented in Asian networks is a Pay-Per-Use model
of services. This model will be difficult to implement in the United States, where the public is used to a service-for-free model (e.g., the Internet).
Conclusions
4G networks may eventually deliver on all the promises. At times, it seems that technological advances are being made on a daily basis. These advances will make high speed data/voice-over-Internet-protocol (VoIP) networks a reality.
In the meantime, it is important for industry to develop a strong 3G offering that is palatable for the general public. Equally as important, industry must ensure that expectations are realistic and that services meet and exceed those expectations.
If all goes according to what the industry envisions, it may be sooner, rather than later that we will see wireless communications evolve. This evolution will give the general public as well as the public safety community amazing functionality from the convenience of a single handheld device.
References
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